Nano-scale systems have demonstrated many novel and interesting optical properties. These systems are extremely important for future photon-based devices among many other applications. Being able to manufacture miniature light sources that have very small spectral width (e.g. lasers) is of utmost importance for science and industrial light.
Many different configurations of nanolasers have been proposed in the literature, such as surface polariton lasing, quantum dots and nano wire lasers etc. However they are either big in size or have large spectral width for the emitted light.
For example D. J. Bergman and M. I. Stockman, Phys. Rev. Lett. 90,027402, 2003, proposed putting a quantum dot close to a nanoparticle to stimulate its plasmon resonance They proposed a coherent near field emission of the system which they called “Spaser” or “Surface Plasmon Amplification by Stimulated Emission of Radiation”.
RU 2249278 C2 discloses a method and dipole nanolaser (DNL) for generation of coherent electromagnetic radiation. The DNL consists of a two-tier system in the form of quantum dots and metallic or semiconductor nanoparticles with a size smaller than the wavelength of the radiation, placed in a transparent medium at a distance from each other. A detailed theoretical study of the DNL conducted by A. S. Rosenthal and Talal Ghannam (Physical Review A 79, 043824, 2009) has shown that the light emitted by the DNL has a very broad spectral width, around 1015 Hz, even larger than the spectral width of the nanoparticle or the exciting element, which means that the system is not lasing at all. This was later corroborated by an experiment conducting by Markus Pfeiffer et al, Nano Lett. 10, 4555-4558, 2010, where the spectral width emitted from gold nanoparticles had a spectral width same as that of the nanoparticle and not less. To reduce the spectral width of the DNL, Rosenthal et al needed to increase the pumping of the quantum dot to unrealistic values, e.g. in the ultraviolet region.